Doctor blade holder

ABSTRACT

A doctor blade holder has a pair of holder members which retain the back edge of a doctor blade between them, one member exerting resilient pressure on the blade to urge it toward the other member through a resilient yieldable strip mounted thereon, the arrangement providing desirable flexibility for the blade and also providing sealing.

United States Patent 11 1 1111 3,854,162 Russell 1' Dec. 17, 1974 [541DOCTOR BLADE HOLDER 2,498,213 2/1950 Ljungquist 15/256.5l 2,987,7486/1961 Scott [75] Inventor: Robert H. Russell, Norfolk, Mass 3,143,4388/1964 Campbell." 73 Assigneez Bird Machine Company, I South 3,255,0386/1966 Coghill 118/126 X Walpole, Mass. Primary Examiner-Harvey C.Hornsby [22] filed 11973 Assistant ExaminerC.. K. Moore [211 Appl.- No.:337,437 Attorney, Agent, or FirmEdgar H. Kent [52] U.S. Cl l5/256.51,100/174, 162/281 57 ST CT v [51] Int. Cl. B411 9/10, D2lg 3/00 581 Fieldof Search l5/256.5l, 256.53, 256.5, A blade hlder has a of 110m" members15/93 R, 2504 250 41; 100/174; /270; which retain the back edge Of adOClOl' blade between 118/261 256 126 34/110421. them, onememberexerting resilient pressure on the 162081 blade to urge it towardthe other member through a v resilient yieldable strip mounted thereon,the arrange- [56] References Cited ment providing desirable flexibilityfor the blade and UNITED STATES PATENTS alsoproviding sealing. 1,883,16710/1932 Vickery l5/256.5l 5 Claims, 3 Drawing Figures 1. Field of theInvention This invention relates to holders for doctor blades,particularly for such blades used for doctoring rolls and the like suchas the rolls and cylinders of paper and pulp making machines.

2. Description of the Prior Art One of the important considerations inthe design of doctor blade holders of the type concerned has been toprovide sufficient firmness of support while yet permitting the blade toflex under the forces applied thereto by the rotating surface engagingits edge. Such flexing is important to permit the blade to adjust itselfto irregular'ities of the surface and in response to differences inamount and adhesion of the material to be doctored from the rotatingsurface.

Numerous holder structures havebeen used or proposed for providing suchflexibility, including: springs attached to the blade and bearingagainst the holder, see e.g. U.S. Pat. No. 3,377,644; inflatable tubesor coil springs on the holder bearing on the blade, see e.g. U.S.

Pat. Nos; 1,566,358, 2,914,788, and 3,529,315; a rocking holderpneumatically cushioned, see e.g. U.S. Pat. No. 3,163,878; and variousloosely held spring plates or spring and keep plates, see eg U.S. Pat.Nos. 2,287,350, 2,890,473, and 3,596,305. All such devices have hadshortcomings of one sort or another such as expense, too many parts, toomuch blade looseness, difficulties of assembly and disassembly, and soon.

With virtually all priorart doctor holders difficulty has beenexperienced with doctored debris wedging its way into the spaces betweenthe blade and the holder, accumulating and packing to such an extent asto seriously impair the normal operation of blade and holder and also tomake it very difficult to remove and replace a blade. U.S. Pat. No.3,526,017 minimizes this problem. by providing asuction system fordebris-removal overlying the blade and holder, but such apparatus isexpensive. In regard to blade removal difficulties, U.S. Pat. No.3,010,134 provides an inflatable cavity between holder jaws to pry themapart, but again such provision is expensive.

SUMMARY or THE INVENTION which-endwise withdrawal and replacement ofblades is facilitated.

In attaining the foregoing objects, theinvention features a blade holderhaving a pair of holder members arranged for mounting on-a support andto receive and retain between them the back portion of a doctor blade,with its front portion protruding from between them so that its bevelededge is in doctoring position against the rotating surface. One of themembers, preferably of spring metal, resiliently urges the bladetotially shown and with a 2 ward the other member and has mountedthereon aresilient, yieldable strip which bears against the blade andthrough which the pressure of the member is exerted- This strip isdeformable under pressures exerted thereon to increase the flexibilityof the blade in the mounting and also acts as a seal between holdermember and blade to inhibit passage of doctored debris between them.Preferably the surface of the strip engaging the blade has a lowcoefficient of friction compared to'the blade surface so that the bladesurface will slip thereon, facilitating endwise withdrawal of bladesfrom,'and their endwise insertion in, theassembled holder.

In a preferred embodiment, one of the holder members is a flat strip ofrelatively inflexible metal having bolt holes at its rearward end formounting on a support, and a beveled forward end. The other holdermember is of relatively flexible and resilient spring steel and has aflat rearward portion with bolt holes arranged to align with the boltholes in the first member so that the two membersare assembled togetherby mounting on the support.'Adjacent the bolt holes and at its forwardend the flexible member is bent at substantially a I right angle, thebent portions and an intervening flat portion forming a channel betweenthe members when assembled.

In such preferred embodiment, the yieldable strip is of plasticcomposition with a longitudinal slot into which the bent forward end ofthe flexible member may be forced to mount the strip on the member, sothat the member urges the strip against the blade under resilientpressure. The infl'exiblegholder member has positioning projectionsextending into the channel. The back end of the blade is insertedbetween the holder members,

with its rearward edge against the positioning p'rojec-- tions and isheld between the members by resilient pressure exerted by the resilientmember through the strip. The blade is provided with lugs which projectinto the channel to engage the strip and prevent undesired forwardremoval of the blade from the holder, although permitting endwisesliding of the blade out of the holder.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is an end view of a preferred embodiment of the holder of theinvention mounted on a support pardoctor blade held therein innon-working position; r

FIG. 2 is a view similarto FIG. 1 showing the blade in working positionagainst a roll; and

FIG. 3 is an explodedpartial perspective view of parts shown assembledin FIGS. 1 and 2. a

In the drawing, the two holder members are designated generally 10 and12, I'CSPCCIIVEIY.'II1 FIGS. 1 and 2 they are shown assembled togetherahd mounted on a support 14 by means of bolts 16 extending throughregistering bolt holes 18 in the rearward part of member 10, and 20 inthe rearward part of member 12, and received in threaded apertures 22 insupport 14. The back portion of a doctor blade 24 is held between themembers with its forward portion protruding between them and with itsbeveled front edge 26 in position for doctoring engagement with thesurface of a roll R partially indicated in FIG. 2, rotating in thedirection of the arrow. It will be understood that the holder members,

the doctor blade and the support extend the full axial length, of theroll surface to be doctored.

Holder member is a flat bar of relatively rigid metal which has abeveled forward end or nose 28. Member 12 has a flat rearward portion 30containing bolt holes which seats on support 14 and against the adjacentsurface portion of member 10. Member 12 has its front portion 32 bent atsubstantially a right angle to the contiguous portion 34. A portion 36,between portions 34'and is similarly bent so that portions 36, 34 and 32form a channel 38 which is between the members when they are assembled.In accordance with the invention, resilient, yieldable strip material,

which may be of a plastic composition, is mounted on front portion 32 ofmember 12. As shown, this material is a single strip 40 formed with alongitudinal slot 42 and is mounted on member 12 by forcing end portion32 of that member into slot 42, spreading the portions of the strip atopposite sides of the slot which firmly grip portion 32 between themadjacent its base to hold strip 40 in place. Strip 40 is deformableunder pressures applied thereto against the blade to increase theflexibility of the mounting. Strip 40 preferably also has a surface witha low coefficient of friction, lower than that of the blade surfacewhich it contacts, so that the blade readily slips on it. A strip ofnylon impregnated with moly-disulfite has been found satisfactory butvarious other compositions or materials can be used.

Member 10 is provided at intervals with flat-headed positioning studs 44which project therefrominto chan-,

nel 38, the stems of these studs engaging the back edge of doctor blade24 to limit its rearward position in the holder. The surface of blade 24opposite its doctoring surface is provided at intervals with bosses 46projecting into channel 38 and so spaced from the back edge of the bladethat they are contiguous to the side of strip 40 when the back edge ofthe blade is against positioning projections 44. Bosses 46 preventforward removal of blade 24 from the holder unless the holder membersare pried apart. Endwise-sliding of the blade from the holder isprevented by cotter pins 48 extending through apertures 50 in holdermember 10 at each end edge of the blade.

Preferably, the back end of the blade is loosely held between member 10and strip 40 on member 12 so that in the non-working position of theblade shown in FIG. 1, the blade is free to pivot on strip 40 in theclockwise direction in FIG. 1 until its rear edge engages the underfaceof member 10, the blade being supported by member 12 on strip 40 at aslight incline. When the blade is placed in a working position against aroll as shown in FIG. 2, it is pivoted in the reverse direction so thatits rear edge is away from member 10, while forwardly of strip 40 theblade engages the front underside of nose 28 of member 10 about which itcan pivot to the extent permitted by limiting'engagement of its rearedge with the heads of studs 44 and the underside of member 1,0. Theedge 26 of the blade is thus resiliently held against the roll by thespring pressure of member 12 cushioned throughstrip 40 urging the bladeto pivot in the clockwise direction in FIG. 2 about its point, ofengagement with the under edge of nose 28. In addition to itscontribution to the flexibility of the mounting, strip 40 is aneffective seal preventing doctored debris from entering the channel 38between the members and so to impair their operation.

Assembly and disassembly of the embodiment shown is relatively simple.The two holder members may be assembled on the support with their boltholes aligned with one another and with the apertures, and the boltsapplied through the holes into the appertures. The doctor blade may thenbe assembled to the holder by sliding its back portion into channel 38between projections 44 and strip 40, and applying cotter pins 48 toprevent further endwise sliding of the blade. For blade replacement onecotter pin is removed, the old blade is pulled out from that end and thenew blade is inserted as just described.

Each holder member may be providedin one piece the full axial length ofthe rotarysurface to be doctored, or either or both may be provided inmultiple sections to be assembled end to end. If both members aresectioned, it is preferred that the section ends of one member alternatebetween section ends of the other, so that the section ends of onemember are overlaid or underlaid by a continuous portion of the othermember. The two holder members may be joined tov gether at their backends if desired, as by welding. However, the separate arrangement shownis preferred since it provides a longer effective lever arm for member12. The doctor blade may be made of metal or of plastic or othersuitable composition.

In case a holder is wanted wherein insertion and removal of the bladecan be readily accomplished from the front, turned up front portion 32of member 12 and strip thereon are cut away at intervals correspondingin spacing to the spacing of bosses 46 to form openings of a depth andwidth sufficient to permit the bosses 46 to pass through the openingswhen a blade is slid from the front between members 10 and 12. Afterinsertion from the front, the blade is slid longitudinally to itsposition determined by cotter pins 48, so that bosses 46 are locatedbetween these openings and accidental frontward dislodgement of theblade will beprevented by engagement by bosses 46 with strip 40 he tweenthe openings.

g I claim: I

1. A holder for a doctor blade for doctoring rolls and the likecomprising: 1

a pair of holder members constructed and arranged to be secured togetherto a support adjacent one of their longitudinal edges with theiropposite edges free for receiving and retaining the back portion of, adoctor blade between them .with its doctoring edge projected beyond themand with one member resiliently urged toward the other member to exertsufficient pressure on said blade to hold it in operative positionagainst the other member;

said one member being formed of resilient metal and being arranged to befastened to the other said member adjacent their edges remote from thedoctoring edge of a said blade received between them so that the otheredge of said one member is flexible toward and away from the other saidmember;

said one member having mounted thereon adjacent said other edge thereofa resilient, yieldable strip material extending longitudinally of saidmember and blade and positioned so that said one member exerts saidpressure on said blade through said material, said material beingdeformable under said pressure;

3. A holder according to claim 1 wherein the blade engaging surface ofsaid strip material has a lower coefficient of friction than the bladesurface engaged thereby.

4. A holder according to claim 1 wherein said other edge of said onemember is bent to extend toward a said blade received between saidmembers with its edge adjacent said blade, and said strip material has alongitudinal slot therein intowhich said other edge of said one memberis received, to mount said material thereon.

5. A holder according to claim 1 wherein said doctor blade is providedwith lugs projecting toward said one member when said blade is receivedbetween said members and contiguous to the rear face of said strip.

1. A holder for a doctor blade for doctoring rolls and the likecomprising: a pair of holder members constructed and arranged to besecured together to a support adjacent one of their longitudinal edgeswith their opposite edges free for receiving and retaining the backportion of a doctor blade between them with its doctoring edge projectedbeyond them and with one member resiliently urged toward the othermember to exert sufficient pressure on said blade to hold it inoperative position against the other member; said one member beingformed of resilient metal and being arranged to be fastened to the othersaid member adjacent their edges remote from the doctoring edge of asaid blade received between them so that the other edge of said onemember is flexible toward and away from the other said member; said onemember having mounted thereon adjacent said other edge thereof aresilient, yieldable strip material extending longitudinally of saidmember and blade and positioned so that said one member exerts saidpressure on said blade through said material, said material beingdeformable under said pressure; and means to secure said holder membersto a said support with said other member preceding said one member inthe direction of rotation of the surface to be doctored.
 2. A holderaccording to claim 1 wherein said one member is spaced sufficiently fromthe other member to permit the blade to pivot on said strip so that itsback edge is movable toward and away from each member.
 3. A holderaccording to claim 1 wherein the blade engaging surface of said stripmaterial has a lower coefficient of friction than the blade surfaceengaged thereby.
 4. A holder according to claim 1 wherein said otheredge of said one member is bent to extend toward a said blade receivedbetween said members with its edge adjacent said blade, and said stripmaterial has a longitudinal slot therein into which said other edge ofsaid one member is received to mount said material thereon.
 5. A holderaccording to claim 1 wherein said doctor blade is provided with lugsprojecting toward said one member when said blade is received betweensaid members and contiguous to the rear face of said strip.